1. Field of the Invention
The present invention relates to a driving tool, and more particularly to a motorized driving tool.
2. Description of the Prior Art
A typical motorized driving tool is shown in FIG. 1 and comprises a shaft 10 driven by a motor 11 which has a spindle extended through a cylinder 12, a screw driver or a socket is engaged to the shaft 10 for driving a fastener such as screw, bolt, nut . . . etc. In order to drive different fasteners, it is required to adjust the torque of the driving tool in some cases, therefore, a cap 13 is rotatably engaged on the cylinder 12 and includes one or more protrusions 130 each having an inclined engaging surface 131, a washer 14, a spring 15, a ring 16 and a number of balls 17 engaged between the cap 13 and the cylinder 12, the washer 14 includes a number of projections 140 extended radially outward for engaging with the engaging surfaces 131 of the protrusions 130 such that the spring 15 can be forced or released by the washer 14 when the cap 13 is rotated. However, when such a driving tool is used for drilling holes in concrete object, the torque of the motor 11 is not enough for driving the shaft 10.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional motorized driving tools.